1. Field of the Invention
The present invention relates to a medical instrument holding apparatus for holding medical instruments, such as endoscopes, surgical instruments, etc., that are used in the surgical removal of tumors in the field of neurosurgery, for example.
2. Description of the Related Art
Modern microsurgery is being frequently performed using operating microscopes for extended observation of fine sites of neurosurgical operations. The observation range of an operating microscope is limited to regions that can be observed through an opening in the cranium. These regions involve dead-angle portions that cannot be viewed through the operating microscope. An endoscope is used to observe these dead-angle portions.
In performing microsurgery, an operator watches an observational image of the endoscope as he/she inserts a surgical instrument into a region to be treated in the cranium. As this is done, the endoscope is supported and fixed by means of a medical instrument holding apparatus that has a plurality of arms and joint portions. Important tissues, such as nerves, blood vessels, etc., are intertwined intricately and minutely in the cranium. Therefore, the endoscope is expected to be designed so that it can be moved finely and smoothly and fixed in a correct position by means of the holding apparatus.
Described in U.S. Pat. No. 5,609,565, for example, is a medical instrument holding apparatus that has a holding portion on its distal end for holding a medical instrument, such as an endoscope. This apparatus has ball joints for joint portions of a plurality of arms and a counterbalance or counterweight on the side opposite the distal end portion that holds the medical instrument. The counterweight is balanced with the medical instrument and the like. Thus, the operator can freely locate the medical instrument in a desired position with a small force. In this apparatus, the joints of the arms are composed of ball joints that can move in the same manner as those of the human body, for example. In consequence, the operator can use the ball joints to operate the medical instrument on the holding portion with a natural feeling of manipulation. Further, the operator can locate the medical instrument in an optimum position, depending on the technique or the site of operation.
Described in Jpn. Pat. Appln. KOKAI Publication No. 7-227398, for example, is a medical instrument holding apparatus in which each of arms that constitute a body-supporting portion is composed of a parallelogrammatic link. In this apparatus, the center of gravity of a medical instrument that is attached to the distal end portion of the supporting portion is aligned with the center of inclination of an L-shaped arm end portion. This apparatus is provided with two counterweights on the side of the body-supporting portion opposite from the side on which the medical instrument is located. The counterweights serve to cancel the weight of the medical instrument and the like. By using the apparatus constructed in this manner, the operator can continually maintain the balanced state of the medical instrument on the distal end portion of the body supporting portion or parallelogrammatic link structure as he/she moves the instrument by means of the counterbalanced arms of the supporting portion. Thus, the operator can easily perform fine adjustment such as the change of the endoscopic field.